In this Jan. 13, 2010 file photo, two young wild horses play while grazing in Reno, Nev. Wild horse protection advocates say the government is rounding up too many mustangs while allowing livestock to feed at taxpayer expense on the same rangeland scientists say is being overgrazed. (Reno Gazette-Journal, Andy Barron)

RENO, Nev. — Tensions bubbled over on the range in a turf battle that has been simmering for decades over one of the icons of the American West and scant forage on arid, high desert lands from Nevada to Wyoming.

With the presence of wild horses continuing to pit animal advocates against ranchers, the U.S. Bureau of Land Management, which is caught in the middle, on Saturday began seizing hundreds of cattle from a longtime rancher that it says are trespassing on public land in southern Nevada.

The action came a day after the agency agreed to remove horses from the range in southwest Utah after Iron County commissioners threatened to take matters in their own hands.

Wild-horse protection advocates say the government is rounding up too many mustangs while allowing livestock to feed at taxpayer expense on the same rangeland scientists say is being overgrazed.

Ranchers say the government refuses to gather enough horses in the herds that double in size every five years while moving to confiscate cattle on lands where their ancestors have operated for more than a century.

The BLM says it's doing all it can, given budget constraints, overflowing holding pens and a distaste for the politically unpopular options of either ending the costly roundups or slaughtering excess horses.

The agency started taking cattle Saturday from Cliven Bundy, who it says has been trespassing on U.S. land without required grazing permits for over 25 years. Bundy doesn't recognize federal authority on land he insists belongs to Nevada.

"These people are thieves," Bundy told The Associated Press on Saturday. "I haven't even started fighting yet. You think I'm going to lay down and just give up. I'm going to fight for the Constitution and state sovereignty."

Asked what actions he planned to take, Bundy replied, "Why don't you wait and see. As I told the BLM and county sheriff, 'I'll do whatever it takes.'"

BLM spokeswoman Kirsten Cannon, in a media conference call Saturday afternoon, said her agency was implementing two federal court orders to remove Bundy's cattle after making repeated efforts to resolve the matter outside court.

Plans call for the removal of some 900 trespassing cattle from 1,200 square miles of land in southern Nevada managed by her agency and the National Park Service over the next three to four weeks, she said.

A federal judge in Las Vegas first ordered Bundy to remove his trespassing cattle in 1998. Similar orders were issued last July and again in October.

"(Bundy's trespassing) is unfair to the thousands of other ranchers who graze livestock in compliance with federal laws and regulations in the West," Cannon said, adding the agencies are working with local and state officials to ensure the removal occurs in a safe manner.

She declined to comment on the number of personnel involved, and was unable to provide a cost estimate for the operation.

Bundy, who said he owns about 500 cows, estimates at least 100 federal agents and other personnel, many of them armed, gathered around the ranch his family has operated since the 1870s southwest of Mesquite a few miles from the Utah line.

"I've tried to stop them for 20 years. I've tried to be legal in the courts. I've tried to do it politically and through the media. Now, it's about down to having to do it as 'We the people,'" he said.

It's a battle that has raged since the 1980s when the Sagebrush Rebellion challenged federal ownership of Nevada rangeland ranchers said was rightfully theirs.

During the past 10 years, horse advocates have been more the aggressors, asking courts to block roundups they say violate the Wild Free-Roaming Horses and Burro Act of 1971. But in recent months, ranchers have again gone back on the attack.

The Nevada Farm Bureau Federation and Nevada Association of Counties sued the government in U.S. District Court in Reno in December seeking to force the BLM to step up roundups and, if necessary, sell excess mustangs for slaughter — something they say is allowed under the law but that the federal agency has resisted.

Earlier this week, a federal magistrate judge in Reno granted horse advocates' request to become a party in that case based on their argument no one else involved — including the BLM — has the horses' best interest in mind.

In Utah, Iron County commissioners had threatened to gather up hundreds of mustangs themselves, saying the horses threaten livestock and wildlife on rangelands already damaged by drought.

"We will take whatever action we have to take to reduce those numbers immediately," Commissioner David Miller told the Salt Lake Tribune.

But BLM State Director Juan Palma, in an email sent Friday to Miller, said he is committed to working with the county in developing a plan to reduce the number of horses, The Spectrum of St. George, Utah, reported.

"Both the BLM and Iron County have a shared interest in the well-being of the range and all who rely in its health. ... Additionally, (we have) our shared interest in the well-being of sustainable populations of our wild horses," Palma wrote.